802.11 mesh architecture

ABSTRACT

A wireless network device comprises a forwarding table and a mesh routing module. The forwarding table stores direct and reverse entries, each including a destination address, a next hop address, and a metric. The metric of the direct entries corresponds to a route from the wireless network device to the destination address. The metric of the reverse entries corresponds to a route from the destination address to the wireless network device. The mesh routing module wirelessly receives route discovery packets and creates corresponding entries in the forwarding table.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/794,383, filed on Apr. 24, 2006. The disclosure of the aboveapplication is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to wireless mesh networks.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

IEEE 802.11, 802.11a, 802.11b, 802.11g, 802.11h, 802.11n, 802.16, and802.20, which are hereby incorporated by reference in their entirety,define operation and implementation of wireless local area networks(WLANs). These standards define modes of operation for WLANs, includingad-hoc and infrastructure.

Referring now to FIG. 1, a functional block diagram of an ad-hocwireless network 100 is depicted. The ad-hoc wireless network 100includes three wireless client stations 104-1, 104-2, and 104-3,although ad-hoc networks with two or more client stations are possible.The client stations 104 together form a basic service set (BSS),identified by a BSS identifier, BSSID. In an ad-hoc network, such as thead-hoc wireless network 100, the client stations 104 communicatedirectly with each other as indicated by the arrows in FIG. 1.

A beacon is periodically transmitted by the client stations 104. Thebeacon includes a timestamp used for synchronization, a beacon interval,and capability information, such as supported transfer rates. Aftertransmission of the beacon, there is an announcement traffic indicationmessage (ATIM) window, the length of which is indicated by the beacon.During the ATIM window, a client station 104 can notify another clientstation 104 that traffic has been buffered for it.

A beacon interval specifies the amount of time before the next beaconwill be transmitted. Based upon the beacon interval, client stations 104can operate in a low power mode until the next beacon is expected.During low power mode, a client station 104 may power down components,such as transceivers, and/or alter operation to conserve power.

The client station 104 may not be able to transmit or receive data whilein low power mode. The client station 104 will resume normal operationin order to receive the beacon, and will remain awake during the ATIMwindow. If the client station 104 receives or transmits based on areceived ATIM, it will stay awake for the remainder of the beaconinterval.

Referring now to FIG. 2, a functional block diagram of an exemplaryinfrastructure mode wireless network 150 is depicted. The infrastructuremode wireless network 150 includes three client stations 154-1, 154-2,and 154-3, which all communicate with a common device, access point (AP)156.

The client stations 154 and AP 156 together form a BSS. In variousimplementations, the BSSID is equal to the MAC address of AP 156. AP 156serves as an intermediary for one client station 154 to communicate withanother client station 154. AP 156 may also communicate with a wirednetwork 158, which in turn may communicate with other BSS's (not shown)or other networks, such as the Internet 160.

AP 156 periodically transmits a beacon to the client stations 154 withinthe BSS. The beacon is a packet or frame of information that informs theclient stations 154 about the capabilities of the BSS and coordinatescommunication within the BSS. The beacon includes the BSSID, the beaconinterval, and a delivery traffic indication message (DTIM). The DTIMserves a function similar to the ATIM of an ad-hoc network.

Referring now to FIG. 3, a functional block diagram of an exemplary meshnetwork 200 is depicted. The mesh network 200 includes specialized meshportals 202-1 and 202-2, which communicate with a network 204, such asthe Internet. The mesh network 200 also includes mesh points 208-1,208-2, 208-3, 208-4, 208-5, and 208-6. The mesh points 208 communicatewith each other according to their physical proximity and signalstrength. The mesh points 208 interface with the mesh portals 202 togain access to the network 204. The mesh portals 202 may relay trafficbetween each other via the network 204.

SUMMARY

A wireless network device comprises a forwarding table and a meshrouting module. The forwarding table stores direct and reverse entries,each including a destination address, a next hop address, and a metric.The metric of the direct entries corresponds to a route from thewireless network device to the destination address. The metric of thereverse entries corresponds to a route from the destination address tothe wireless network device. The mesh routing module wirelessly receivesroute discovery packets and creates corresponding entries in theforwarding table.

In other features, the mesh routing module wirelessly receives a firstroute discovery packet including a metric and a source address from asecond wireless network device and creates a reverse entry in theforwarding table. The next hop address of the reverse entry is set to anaddress of the second wireless network device, the destination addressof the reverse entry is set to the source address of the first routediscovery packet, and the metric of the reverse entry is set to themetric of the first route discovery packet.

In further features, the mesh routing module wirelessly receives a routereply packet including a reply destination address, identifies ones ofthe reverse entries that have the reply destination address, andtransmits the route reply packet to the next hop address of a selectedone of the identified reverse entries. The mesh routing module selectsthe selected one of the identified reverse entries based upon themetrics of the identified reverse entries. The reverse entries eachinclude a sequence number. The mesh routing module sets the sequencenumber of the reverse entry to a sequence number received in the firstroute discovery packet.

In still other features, the route reply packet includes a replysequence number. The mesh routing module chooses ones of the identifiedreverse entries that have the reply sequence number and selects one ofthe chosen reverse entries based upon the metrics of the chosen reverseentries. The mesh routing module receives a route request for arequested destination address, identifies ones of the direct entriesthat have the requested destination address, and selectively responds tothe route request with the next hop address of a selected one of theidentified direct entries.

In other features, the mesh routing module selects the selected one ofthe identified direct entries based upon the metrics of the identifieddirect entries. The direct entries of the forwarding table include anexpiration indicator. The mesh routing module selects the selected oneof the identified direct entries based upon the expiration indicators ofthe identified direct entries.

In further features, the mesh routing module transmits a route discoverypacket including a cumulative metric to a second wireless networkdevice, determines the cumulative metric based upon a received metricand a link metric, and determines the link metric based upon a state ofcharge of the wireless network device and a transmission parameter ofthe route discovery packet. The link metric increases as the state ofcharge decreases. The transmission parameter comprises energy used totransmit the route discovery packet. The link metric is proportional tothe energy used and inversely related to the state of charge. The meshrouting module transmits the route discovery packet using increasingamounts of energy.

A method for a wireless network device comprises wirelessly receivingroute discovery packets; and storing direct and reverse entries in aforwarding table based upon the route discovery packets, each of theentries including a destination address, a next hop address, and ametric. The metric of the direct entries corresponds to a route from thewireless network device to the destination address. The metric of thereverse entries corresponds to a route from the destination address tothe wireless network device.

In other features, the method further comprises receiving a first routediscovery packet including a metric and a source address from a firstwireless network device; and creating a reverse entry in the forwardingtable. The next hop address of the reverse entry is set to an address ofthe first wireless network device, the destination address of thereverse entry is set to the source address of the first route discoverypacket, and the metric of the reverse entry is set to the metric of thefirst route discovery packet.

In further features, the method further comprises receiving a routereply packet including a reply destination address wirelessly;identifying ones of the reverse entries that have the reply destinationaddress; and transmitting the route reply packet to the next hop addressof a selected one of the identified reverse entries. The selected one ofthe identified reverse entries is selected based upon the metrics of theidentified reverse entries.

In still other features, the reverse entries each include a sequencenumber, and further comprises setting the sequence number of the reverseentry to a sequence number received in the first route discovery packet.The route reply packet includes a reply sequence number, and furthercomprises choosing ones of the identified reverse entries that have thereply sequence number; and selecting one of the chosen reverse entriesbased upon the metrics of the chosen reverse entries.

In other features, the method further comprises receiving a routerequest for a requested destination address; identifying ones of thedirect entries that have the requested destination address; andselectively responding to the route request with the next hop address ofa selected one of the identified direct entries. The selected one of theidentified direct entries is selected based upon the metrics of theidentified direct entries. The direct entries of the forwarding tableinclude an expiration indicator. The selected one of the identifieddirect entries is selected based upon the expiration indicators of theidentified direct entries.

In further features, the method further comprises receiving a firstroute discovery packet including a metric; determining a link metricbased upon a state of charge of the wireless network device and atransmission parameter of a second route discovery packet; determining acumulative metric based upon a received metric and the link metric; andtransmitting the second route discovery packet wirelessly to a firstwireless network device, the second route discovery packet including thecumulative metric.

In still other features, the link metric increases as the state ofcharge decreases. The transmission parameter comprises energy used totransmit the second route discovery packet. The link metric isproportional to the energy used and inversely related to the state ofcharge. The method further comprises transmitting the second routediscovery packet using increasing amounts of energy.

A computer program stored for use by a processor for operating awireless network device comprises wirelessly receiving route discoverypackets; and storing direct and reverse entries in a forwarding tablebased upon the route discovery packets, each of the entries including adestination address, a next hop address, and a metric. The metric of thedirect entries corresponds to a route from the wireless network deviceto the destination address. The metric of the reverse entriescorresponds to a route from the destination address to the wirelessnetwork device.

In other features, the computer program further comprises receiving afirst route discovery packet including a metric and a source addressfrom a first wireless network device; and creating a reverse entry inthe forwarding table. The next hop address of the reverse entry is setto an address of the first wireless network device, the destinationaddress of the reverse entry is set to the source address of the firstroute discovery packet, and the metric of the reverse entry is set tothe metric of the first route discovery packet.

In further features, the computer program further comprises receiving aroute reply packet including a reply destination address wirelessly;identifying ones of the reverse entries that have the reply destinationaddress; and transmitting the route reply packet to the next hop addressof a selected one of the identified reverse entries. The selected one ofthe identified reverse entries is selected based upon the metrics of theidentified reverse entries.

In still other features, the reverse entries each include a sequencenumber, and further comprises setting the sequence number of the reverseentry to a sequence number received in the first route discovery packet.The route reply packet includes a reply sequence number, and furthercomprises choosing ones of the identified reverse entries that have thereply sequence number; and selecting one of the chosen reverse entriesbased upon the metrics of the chosen reverse entries.

In other features, the computer program further comprises receiving aroute request for a requested destination address; identifying ones ofthe direct entries that have the requested destination address; andselectively responding to the route request with the next hop address ofa selected one of the identified direct entries. The selected one of theidentified direct entries is selected based upon the metrics of theidentified direct entries. The direct entries of the forwarding tableinclude an expiration indicator. The selected one of the identifieddirect entries is selected based upon the expiration indicators of theidentified direct entries.

In further features, the computer program further comprises receiving afirst route discovery packet including a metric; determining a linkmetric based upon a state of charge of the wireless network device and atransmission parameter of a second route discovery packet; determining acumulative metric based upon a received metric and the link metric; andtransmitting the second route discovery packet wirelessly to a firstwireless network device, the second route discovery packet including thecumulative metric.

In still other features, the link metric increases as the state ofcharge decreases. The transmission parameter comprises energy used totransmit the second route discovery packet. The link metric isproportional to the energy used and inversely related to the state ofcharge. The computer program further comprises transmitting the secondroute discovery packet using increasing amounts of energy.

A wireless network device comprises forwarding table means for storingdirect and reverse entries each including a destination address, a nexthop address, and a metric. The metric of the direct entries correspondsto a route from the wireless network device to the destination address.The metric of the reverse entries corresponds to a route from thedestination address to the wireless network device; and mesh routingmeans for wirelessly receiving route discovery packets and for creatingcorresponding entries in the forwarding table means.

In other features, the mesh routing means wirelessly receives a firstroute discovery packet including a metric and a source address from asecond wireless network device and creates a reverse entry in theforwarding table means. The next hop address of the reverse entry is setto an address of the second wireless network device, the destinationaddress of the reverse entry is set to the source address of the firstroute discovery packet, and the metric of the reverse entry is set tothe metric of the first route discovery packet.

In further features, the mesh routing means wirelessly receives a routereply packet including a reply destination address, identifies ones ofthe reverse entries that have the reply destination address, andtransmits the route reply packet to the next hop address of a selectedone of the identified reverse entries. The mesh routing means selectsthe selected one of the identified reverse entries based upon themetrics of the identified reverse entries.

In still other features, the reverse entries each include a sequencenumber. The mesh routing means sets the sequence number of the reverseentry to a sequence number received in the first route discovery packet.The route reply packet includes a reply sequence number. The meshrouting means chooses ones of the identified reverse entries that havethe reply sequence number and selects one of the chosen reverse entriesbased upon the metrics of the chosen reverse entries.

In other features, the mesh routing means receives a route request for arequested destination address, identifies ones of the direct entriesthat have the requested destination address, and selectively responds tothe route request with the next hop address of a selected one of theidentified direct entries. The mesh routing means selects the selectedone of the identified direct entries based upon the metrics of theidentified direct entries. The direct entries of the forwarding tablemeans include an expiration indicator. The mesh routing means selectsthe selected one of the identified direct entries based upon theexpiration indicators of the identified direct entries.

In further features, the mesh routing means transmits a route discoverypacket including a cumulative metric to a second wireless networkdevice, determines the cumulative metric based upon a received metricand a link metric, and determines the link metric based upon a state ofcharge of the wireless network device and a transmission parameter ofthe route discovery packet.

In still other features, the link metric increases as the state ofcharge decreases. The transmission parameter comprises energy used totransmit the route discovery packet. The link metric is proportional tothe energy used and inversely related to the state of charge. The meshrouting means transmits the route discovery packet using increasingamounts of energy.

A wireless network device comprises a physical layer (PHY) module thatsends and receives packets wirelessly; a first media access control(MAC) module that wirelessly communicates with a second wireless networkdevice in an ad-hoc mode via the PHY module; and a second MAC modulethat wirelessly communicates with an access point in an infrastructuremode via the PHY module.

In other features, the wireless network device further comprises abridge module that facilitates transmission of packets between the firstMAC module and the second MAC module. The wireless network devicefurther comprises a physical dispatcher module that directs packets fromthe PHY module to one of the first MAC module and the second MAC module.The second MAC module operates according to IEEE 802.11.

In further features, the second MAC module is selectively deactivatedwhen the wireless network device is not within range of the accesspoint. The first MAC module communicates with the second wirelessnetwork device using packets including immediate source and destinationaddresses and final source and destination addresses. The wirelessnetwork device replies to an Address Resolution Protocol (ARP) requestreceived from the access point, the ARP request requesting an address ofthe second wireless network device.

In still other features, the wireless network device further comprises aforwarding table that includes destination entries and best next hopentries. The destination entries each include a destination addressfield and a best next hop field, the best next hop entries each includea receiver address field, and the best next hop field of each of thedestination entries points to one of the best next hop entries. The bestnext hop entries each include a power information field corresponding toa power state of a wireless network device designated by the receiveraddress field.

In other features, the destination entries each include a metric field,and further comprises a mesh routing module that communicates with thefirst MAC module and that populates the forwarding table. The metricfield is based upon an energy cost for transmitting a packet along acorresponding route. The energy cost is calculated with a variabledependence upon state of charge of wireless network devices along thecorresponding route.

A method for a wireless network device comprises wirelesslycommunicating with a first wireless network device in an ad-hoc mode viaa physical layer (PHY) module; and wirelessly communicating with anaccess point in an infrastructure mode via the PHY module.

In other features, the method further comprises operating in theinfrastructure mode according to IEEE 802.11. The method furthercomprises selectively deactivating the infrastructure mode when out ofrange of the access point. The method further comprises communicatingwith the first wireless network device using packets including immediatesource and destination addresses and final source and destinationaddresses.

In further features, the method further comprises replying to an AddressResolution Protocol (ARP) request received from the access point, theARP request requesting an address of the first wireless network device.The method further comprises storing destination entries and best nexthop entries in a forwarding table. The destination entries each includea destination address field and a best next hop field, the best next hopentries each include a receiver address field, and the best next hopfield of each of the destination entries points to one of the best nexthop entries.

In still other features, the best next hop entries each include a powerinformation field corresponding to a power state of a wireless networkdevice designated by the receiver address field. The destination entrieseach include a metric field. The metric field is based upon an energycost for transmitting a packet along a corresponding route. The energycost is calculated with a variable dependence upon state of charge ofwireless network devices along the corresponding route.

A computer program stored for use by a processor for operating awireless network device comprises wirelessly communicating with a firstwireless network device in an ad-hoc mode via a physical layer (PHY)module; and wirelessly communicating with an access point in aninfrastructure mode via the PHY module.

In other features, the computer program further comprises operating inthe infrastructure mode according to IEEE 802.11. The computer programfurther comprises selectively deactivating the infrastructure mode whenout of range of the access point. The computer program further comprisescommunicating with the first wireless network device using packetsincluding immediate source and destination addresses and final sourceand destination addresses.

In further features, the computer program further comprises replying toan Address Resolution Protocol (ARP) request received from the accesspoint, the ARP request requesting an address of the first wirelessnetwork device. The computer program further comprises storingdestination entries and best next hop entries in a forwarding table. Thedestination entries each include a destination address field and a bestnext hop field, the best next hop entries each include a receiveraddress field, and the best next hop field of each of the destinationentries points to one of the best next hop entries.

In still other features, the best next hop entries each include a powerinformation field corresponding to a power state of a wireless networkdevice designated by the receiver address field. The destination entrieseach include a metric field. The metric field is based upon an energycost for transmitting a packet along a corresponding route. The energycost is calculated with a variable dependence upon state of charge ofwireless network devices along the corresponding route.

A wireless network device comprises physical layer (PHY) means forsending and receiving packets wirelessly; first media access control(MAC) means for wirelessly communicating with a second wireless networkdevice in an ad-hoc mode via the PHY means; and second MAC means forwirelessly communicating with an access point in an infrastructure modevia the PHY means.

In other features, the wireless network device further comprisesbridging means for facilitating transmission of packets between thefirst MAC means and the second MAC means. The bridging means selectivelytransmits a packet to the second MAC means when a destination address ofthe packet corresponds to a wireless network device in communicationwith the access point. The wireless network device further comprisesphysical dispatching means for directing packets from the PHY means toone of the first MAC means and the second MAC means.

In further features, the second MAC means operates according to IEEE802.11. The second MAC means is selectively deactivated when thewireless network device is not within range of the access point. Thefirst MAC means communicates with the second wireless network deviceusing packets including immediate source and destination addresses andfinal source and destination addresses. The wireless network devicereplies to an Address Resolution Protocol (ARP) request received fromthe access point, the ARP request requesting an address of the secondwireless network device.

In still other features, the wireless network device further comprisesforwarding table means for storing destination entries and best next hopentries. The destination entries each include a destination addressfield and a best next hop field, the best next hop entries each includea receiver address field, and the best next hop field of each of thedestination entries points to one of the best next hop entries. The bestnext hop entries each include a power information field corresponding toa power state of a wireless network device designated by the receiveraddress field.

In other features, the destination entries each include a metric field,and further comprises mesh routing means that communicates with thefirst MAC means and that populates the forwarding table means. Themetric field is based upon an energy cost for transmitting a packetalong a corresponding route. The energy cost is calculated with avariable dependence upon state of charge of wireless network devicesalong the corresponding route.

A wireless network device comprises a physical layer (PHY) module thatsends and receives packets wirelessly; and a mesh routing module thatreceives a first packet including a metric and a source address from asecond wireless network device via the PHY module, that transmits asecond packet including a cumulative metric to a third wireless networkdevice via the PHY module, that determines the cumulative metric basedupon the metric from the first packet and a link metric, and thatdetermines the link metric based upon a state of charge of the wirelessnetwork device and a transmission parameter of the second packet.

In other features, the link metric increases as the state of chargedecreases. The transmission parameter comprises energy used to transmitthe second packet. The link metric is proportional to the energy usedand inversely related to the state of charge. The mesh routing moduletransmits the second packet using increasing amounts of energy.

In further features, the wireless network device further comprises aforwarding table that stores direct and reverse entries each including adestination address, a next hop address, and a metric. The metric of thedirect entries corresponds to a route from the wireless network deviceto the destination address. The metric of the reverse entriescorresponds to a route from the destination address to the wirelessnetwork device.

In still other features, the mesh routing module creates a reverse entryin the forwarding table based on the first packet. The next hop addressof the reverse entry is set to an address of the second wireless networkdevice, the destination address of the reverse entry is set to thesource address of the first packet, and the metric of the reverse entryis set to the metric of the first packet.

In other features, the mesh routing module receives a route reply packetincluding a reply destination address via the PHY module, identifiesones of the reverse entries that correspond to the reply destinationaddress, and transmits the reply packet to the next hop address of aselected one of the identified reverse entries. The mesh routing moduleselects the selected one of the identified reverse entries based uponthe metrics of the identified reverse entries.

In further features, the reverse entries each include a sequence numberassociated with the destination address. The reply packet includes areply sequence number, the mesh routing module chooses ones of theidentified reverse entries having the reply sequence number, and themesh routing module selects one of the chosen reverse entries based uponthe metrics of the chosen reverse entries.

In still other features, the mesh routing module receives a routerequest for a requested destination address, identifies ones of thedirect entries having the requested destination address, and responds tothe route request with the next hop address of a selected one of theidentified direct entries. The mesh routing module selects the selectedone of the identified direct entries based upon the metrics of theidentified direct entries. The direct entries of the forwarding tableinclude an expiration indicator. The mesh routing module selects theselected one of the identified direct entries based upon the expirationindicators of the identified direct entries.

A method for a wireless network device comprises receiving a firstpacket wirelessly from a first wireless network device, the first packetincluding a metric and a source address; determining a link metric basedupon a state of charge of the wireless network device and a transmissionparameter of a second packet; determining a cumulative metric based uponthe metric from the first packet and the link metric; and transmittingthe second packet wirelessly to a second wireless network device, thesecond packet including the cumulative metric.

In other features, the link metric increases as the state of chargedecreases. The transmission parameter comprises energy used to transmitthe second packet. The link metric is proportional to the energy usedand inversely related to the state of charge. The method furthercomprises transmitting the second packet using increasing amounts ofenergy.

In further features, the method further comprises storing direct andreverse entries in a forwarding table, each of the entries including adestination address, a next hop address, and a metric. The metric of thedirect entries corresponds to a route from the wireless network deviceto the destination address. The metric of the reverse entriescorresponds to a route from the destination address to the wirelessnetwork device.

In still other features, the method further comprises creating a reverseentry in the forwarding table based on the first packet. The next hopaddress of the reverse entry is set to an address of the first wirelessnetwork device, the destination address of the reverse entry is set tothe source address of the first packet, and the metric of the reverseentry is set to the metric of the first packet.

In other features, the method further comprises receiving a route replypacket including a reply destination address from the second wirelessnetwork device; identifying ones of the reverse entries that correspondto the reply destination address; and transmitting the reply packet tothe next hop address of a selected one of the identified reverseentries. The selected one of the identified reverse entries is selectedbased upon the metrics of the identified reverse entries.

In further features, the reverse entries each include a sequence numberassociated with the destination address. The reply packet includes areply sequence number, and further comprises choosing ones of theidentified reverse entries having the reply sequence number; andselecting one of the chosen reverse entries based upon the metrics ofthe chosen reverse entries.

In still other features, the method further comprises receiving a routerequest for a requested destination address; identifying ones of thedirect entries having the requested destination address; and respondingto the route request with the next hop address of a selected one of theidentified direct entries. The selected one of the identified directentries is selected based upon the metrics of the identified directentries. The direct entries of the forwarding table include anexpiration indicator. The selected one of the identified direct entriesis selected based upon the expiration indicators of the identifieddirect entries.

A computer program stored for use by a processor for operating awireless network device comprises receiving a first packet wirelesslyfrom a first wireless network device, the first packet including ametric and a source address; determining a link metric based upon astate of charge of the wireless network device and a transmissionparameter of a second packet; determining a cumulative metric based uponthe metric from the first packet and the link metric; and transmittingthe second packet wirelessly to a second wireless network device, thesecond packet including the cumulative metric.

In other features, the link metric increases as the state of chargedecreases. The transmission parameter comprises energy used to transmitthe second packet. The link metric is proportional to the energy usedand inversely related to the state of charge. The computer programfurther comprises transmitting the second packet using increasingamounts of energy.

In further features, the computer program further comprises storingdirect and reverse entries in a forwarding table, each of the entriesincluding a destination address, a next hop address, and a metric. Themetric of the direct entries corresponds to a route from the wirelessnetwork device to the destination address. The metric of the reverseentries corresponds to a route from the destination address to thewireless network device.

In still other features, the computer program further comprises creatinga reverse entry in the forwarding table based on the first packet. Thenext hop address of the reverse entry is set to an address of the firstwireless network device, the destination address of the reverse entry isset to the source address of the first packet, and the metric of thereverse entry is set to the metric of the first packet.

In other features, the computer program further comprises receiving aroute reply packet including a reply destination address from the secondwireless network device; identifying ones of the reverse entries thatcorrespond to the reply destination address; and transmitting the replypacket to the next hop address of a selected one of the identifiedreverse entries. The selected one of the identified reverse entries isselected based upon the metrics of the identified reverse entries.

In further features, the reverse entries each include a sequence numberassociated with the destination address. The reply packet includes areply sequence number, and further comprises choosing ones of theidentified reverse entries having the reply sequence number; andselecting one of the chosen reverse entries based upon the metrics ofthe chosen reverse entries.

In still other features, the computer program further comprisesreceiving a route request for a requested destination address;identifying ones of the direct entries having the requested destinationaddress; and responding to the route request with the next hop addressof a selected one of the identified direct entries. The selected one ofthe identified direct entries is selected based upon the metrics of theidentified direct entries. The direct entries of the forwarding tableinclude an expiration indicator. The selected one of the identifieddirect entries is selected based upon the expiration indicators of theidentified direct entries.

A wireless network device comprises physical layer (PHY) means forsending and receiving packets wirelessly; and mesh routing means forreceiving a first packet including a metric and a source address from asecond wireless network device via the PHY means, for transmitting asecond packet including a cumulative metric to a third wireless networkdevice via the PHY means, for determining the cumulative metric basedupon the metric from the first packet and a link metric, and fordetermining the link metric based upon a state of charge of the wirelessnetwork device and a transmission parameter of the second packet.

In other features, the link metric increases as the state of chargedecreases. The transmission parameter comprises energy used to transmitthe second packet. The link metric is proportional to the energy usedand inversely related to the state of charge. The mesh routing meanstransmits the second packet using increasing amounts of energy.

In further features, the wireless network device further comprisesforwarding table means for storing direct and reverse entries eachincluding a destination address, a next hop address, and a metric. Themetric of the direct entries corresponds to a route from the wirelessnetwork device to the destination address. The metric of the reverseentries corresponds to a route from the destination address to thewireless network device.

In still other features, the mesh routing means creates a reverse entryin the forwarding table means based on the first packet. The next hopaddress of the reverse entry is set to an address of the second wirelessnetwork device, the destination address of the reverse entry is set tothe source address of the first packet, and the metric of the reverseentry is set to the metric of the first packet.

In other features, the mesh routing means receives a route reply packetincluding a reply destination address via the PHY means, identifies onesof the reverse entries that correspond to the reply destination address,and transmits the reply packet to the next hop address of a selected oneof the identified reverse entries. The mesh routing means selects theselected one of the identified reverse entries based upon the metrics ofthe identified reverse entries.

In further features, the reverse entries each include a sequence numberassociated with the destination address. The reply packet includes areply sequence number. The mesh routing means chooses ones of theidentified reverse entries having the reply sequence number. The meshrouting means selects one of the chosen reverse entries based upon themetrics of the chosen reverse entries.

In still other features, the mesh routing means receives a route requestfor a requested destination address, identifies ones of the directentries having the requested destination address, and responds to theroute request with the next hop address of a selected one of theidentified direct entries. The mesh routing means selects the selectedone of the identified direct entries based upon the metrics of theidentified direct entries. The direct entries of the forwarding tablemeans include an expiration indicator. The mesh routing means selectsthe selected one of the identified direct entries based upon theexpiration indicators of the identified direct entries.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a computer readable medium such asbut not limited to memory, non-volatile data storage and/or othersuitable tangible storage mediums.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the disclosure, are intended forpurposes of illustration only and are not intended to limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an ad-hoc wireless networkaccording to the prior art;

FIG. 2 is a functional block diagram of an exemplary infrastructure modewireless network according to the prior art;

FIG. 3 is a functional block diagram of an exemplary mesh networkaccording to the prior art;

FIG. 4 is a functional block diagram of an exemplary mesh networkaccording to the principles of the present disclosure;

FIG. 5 is a flowchart depicting exemplary steps performed in sending apacket through the mesh network;

FIG. 6 is a functional block diagram depicting exemplary components ofthe mesh network and the routing of two exemplary packets within themesh network;

FIG. 7A is a flowchart depicting exemplary steps taken in sending apacket from mesh node X to node A;

FIG. 7B is a flowchart depicting exemplary steps taken in sending apacket from node A to mesh node X;

FIG. 8 is a functional block diagram of a network module of an exemplarymesh node;

FIG. 9 is a flowchart depicting exemplary operation of the networkmodule in transmitting a packet;

FIG. 10 is a flowchart depicting exemplary operation of the networkmodule in receiving a packet;

FIG. 11 is a graphical and tabular representation of an exemplary routediscovery process;

FIG. 12A is a graphical depiction of route discovery messages in anexemplary mesh network;

FIG. 12B is a tabular representation of forwarding table entries madeduring the route discovery process of FIG. 12A;

FIG. 13A is a table depicting an exemplary format of a route request(RREQ) packet;

FIG. 13B is a table depicting an exemplary format of a route reply(RREP) packet;

FIG. 14 is a flowchart depicting exemplary operation of a mesh node inreceiving an RREQ packet;

FIG. 15 is a flowchart depicting exemplary operation of a mesh node ingenerating an RREP packet;

FIG. 16 is a flowchart depicting exemplary operation of a mesh node inreceiving an RREP packet;

FIG. 17 is a functional block diagram depicting an exemplaryimplementation of a forwarding table;

FIG. 18 is a table depicting exemplary forwarding table contents;

FIG. 19 is a table depicting exemplary configuration parameters foroperation of a mesh node;

FIG. 20A is a functional block diagram of a vehicle control system;

FIG. 20B is a functional block diagram of a cellular phone; and

FIG. 20C is a functional block diagram of a media player.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

As used herein, the term module refers to an Application SpecificIntegrated Circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

Referring now to FIG. 4, a functional block diagram of an exemplary meshnetwork 250 according to the principles of the present disclosure ispresented. The mesh network 250 includes access points (APs) 252-1 and252-2 and mesh nodes 254-1, 254-2, 254-3, 254-4, 254-5, and 254-6. AP252-1 communicates with a wired node 256 via a wired protocol, such asIEEE 802.3. For purposes of clarity, wired node 256 is labeled as A, AP252-1 is labeled as AP, and mesh nodes 254-1, 254-5, and 254-6 arelabeled as C, D, and X, respectively.

In the mesh network 250, mesh nodes 254 communicate with each other inmesh mode, which may be similar to the ad-hoc mode defined by IEEE802.11, with modifications as described herein. Mesh mode operation isdescribed in more detail with respect to Draft IEEE standard P802.11s,which is hereby incorporated by reference in its entirety. The meshnodes 254 communicate with the APs 252 in infrastructure mode. Becausethe APs 252 naturally operate in infrastructure mode, they do not needto be modified to interact with the mesh nodes 254.

Mesh nodes 254 that are in communication with the APs 252 (in thisexample, mesh nodes 254-1, 254-2, and 254-3) provide translation betweeninfrastructure mode used by the APs 252 and mesh mode used by the othermesh nodes 254. In this mode of operation, mesh nodes 254-1, 254-2, and254-3 can be referred to as mesh portals. In various implementations,any of the mesh nodes 254 can act as mesh portals when in communicationwith one of the APs 252.

Referring now to FIG. 5, a flowchart depicts exemplary steps performedin sending a packet through the mesh network 250. Control begins in step300, where a mesh node (such as one of the mesh nodes 254) creates apacket. The destination media access control (MAC) address of the packetmay be determined based upon a destination internet protocol (IP)address for the packet using such technologies as address resolutionprotocol (ARP). The destination IP address may be obtained throughdomain name system (DNS) resolution of a domain name requested by anapplication.

Control continues in step 302, where the mesh node determines, asexplained in further detail below, the first node in the best route tothe destination address. The mesh node then sends the packet to thatfirst node. Control continues in step 304, where the mesh node thatreceives the packet checks whether it is the final destination of thepacket. If so, control ends; otherwise, control transfers to step 306.In various implementations, the final destination of the packet includesa layer 2 address. The packet may also include an ultimate layer 3destination address. In step 306, if the receiver is acting as a meshportal, control transfers to step 308; otherwise, control transfers tostep 310.

In step 310, the mesh node forwards the packet to the next mesh node inthe best route to the final destination, and control returns to step304. In step 308, the mesh portal determines if the final destination iswithin the mesh network. Control may initiate a mesh route discovery todetermine if the final destination is within the mesh network. If thefinal destination is within the mesh network, control transfers to step310; otherwise, control transfers to step 311.

In step 311, the mesh portal forwards the packet to the AP. Controlcontinues in step 312, where the AP determines if it is the finaldestination of the packet. If so, control ends; otherwise, controlcontinues in step 314. In step 314, the AP bridges the packet to asecond interface. This second interface may implement IEEE 802.3, andmay be part of a distribution system (DS). The packet has now left themesh network, and control ends.

Referring now to FIG. 6, a functional block diagram depicts exemplaryimplementations of selected components of the mesh network 250 and therouting of two exemplary packets within the mesh network 250. Selecteddevices from FIG. 4 are shown, including mesh node D 254-5, mesh portalC 254-1, AP 252-1, and node A 256.

Mesh portal C 254-1 includes an 802.11 mesh mode (referred tohereinafter as 802.11mm) interface 352 and an IEEE 802.11 infrastructureinterface 354. The interfaces 352 and 354 are connected via a bridge356. Mesh node D 254-5 may be a mesh portal, such as mesh portal C254-1, operating in a mode where the IEEE 802.11 interface and thebridge are deactivated. In this way, mesh nodes can become mesh portalswhen they are within range of an AP.

Mesh node D 254-5 includes an 802.11mm interface 360. Mesh node D 254-5includes an IP routing layer 362, which communicates with the 802.11mminterface 360. AP 252-1 includes an IEEE 802.11 infrastructure interface364, which is in communication with the IEEE 802.11 infrastructureinterface 354 of mesh portal C 254-1.

AP 252-1 may also include a wired interface 366, which communicates witha wired interface 370 of node A 256. The wired interfaces 366 and 370may implement IEEE 802.3. The interfaces 364 and 366 of AP 252-1 areconnected via a bridge 372. AP 252-1 may additionally serve as a routinggateway, and may consequently include an IP routing layer 374. Node A256 may include wired and/or wireless interfaces (not shown), whichcommunicate with the wired interface 370 via an IP routing layer 376.

In order for mesh node X 254-6 (not shown in FIG. 6) to send a packet tonode A 256, node X 254-6 sends a packet to the first hop on the bestroute to node A 256. Mesh node D 254-4 may be a hop on the best route tonode A 256, and so receives the packet. Mesh node D 254-5 forwards thepacket, depicted graphically in FIG. 6 at 380, to mesh portal C 254-1.The packet 380 may contain four addresses, such as is described in IEEE802.11 for packets sent within a distribution system (DS).

The packet 380 includes an encapsulated IP payload 382 and a layer 2(MAC) header, of which four addresses 384-1, 384-2, 384-3, and 384-4 areshown. Addresses 384-1 and 384-2 are the final layer 2 source anddestination, respectively. In this case, the original source is meshnode X 254-6 and the final destination is node A 256. Addresses 384-3and 384-4 are immediate source and destination addresses, respectively,also called transmitter and receiver addresses, respectively.

The packet 380 is received by the 802.11mm interface 352 of mesh portalC 254-1. The bridge 356 receives the packet 380 from the 802.11mminterface 352. The bridge 356 then determines from which interface thepacket should be sent. In various implementations, the bridge 356creates address tables by passively monitoring traffic, such as addressresolution protocol (ARP) messages. The bridge 356 determines that thepacket 380 should be sent from the IEEE 802.11 infrastructure interface354. The IEEE 802.11 infrastructure interface 354 modifies the headerinformation of the packet 380, thereby creating a new packet 390.

The packet 390 includes the encapsulated IP payload 382 and a layer 2header, of which the BSSID 392 and destination and source addresses394-1 and 394-2 are shown. In various implementations, the BSSID 392 isthe MAC address of AP 252-1, denoted as AP in FIG. 6. The packet 390 isreceived by AP 252-1 at its IEEE 802.11 infrastructure interface 364.The packet is passed to the bridge 372. The bridge 372, in turn,determines from which interface the packet 390 should be sent. In thiscase, the packet is destined for node A 256, which is accessible on thewired interface 366.

The bridge 372 passes the packet 390 to the wired interface 366, whichmodifies the header information of the packet 390, creating a new packet400. The packet 400 includes the encapsulated IP payload 382 and a layer2 header, of which source and destination addresses 402-1 and 402-2 areshown. The packet 400 is received by node A 256. Node A 256 may act as agateway to an external network, such as the Internet. Node A 256 may bethe final layer 2 destination of the packet, while the ultimatedestination of the packet is stored in layer 3 (such as in a header ofthe encapsulated IP payload 382).

Node A 256 can reply by sending a packet to mesh node X 254-6. Node A256 sends a packet 410 to AP 252-1. AP 252-1 forwards a modified packet412, based upon the packet 410, to mesh portal C 254-1. Mesh portal C254-1 forwards a modified packet 414, based upon the packet 412, to meshnode D 254-5. This route assumes that mesh portal C 254-1 has determinedthat mesh node D 254-5 is the best next hop to reach mesh node X 254-6.Mesh node D 254-5 then forwards a modified version of the packet 414 onto mesh node X 254-6.

Referring now to FIG. 7A, a flowchart depicts exemplary steps performedin sending a packet from mesh node X 254-6 to node A 256. Control beginsin step 450, where mesh node X 254-6 creates a packet with a finaldestination of node A 256. In step 452, mesh node X 254-6 determines thefirst hop on the best route to node A 256, a process described infurther detail below. Control continues in step 454, where mesh node X254-6 sends a 4-address IEEE 802.11 packet to mesh node D 254-5. In step456, mesh node D 254-5 determines the next hop in the best route to nodeA 256.

Control continues in step 458, where mesh node D 254-5 sends a 4-addressIEEE 802.11 packet to mesh portal C 254-1. In step 460, mesh portal C254-1 determines that node A 256 is accessible via its IEEE 802.11infrastructure interface 354. Control continues in step 462, where meshportal C 254-1 sends a 3-address IEEE 802.11 packet to AP 252-1. In step464, AP 252-1 determines that node A is accessible via its wiredinterface 366. In step 466, AP 252-1 sends a 2-address packet to node A256, and control ends.

Referring now to FIG. 7B, a flowchart depicts exemplary steps performedin sending a packet from node A 256 to mesh node X 254-6. Control beginsin step 480, where node A 256 creates a packet having an ultimate layer3 destination address of mesh node X 254-6. Node A 256 may determine theMAC address of mesh node X 254-6 from the ultimate layer 3 destinationaddress by sending an address resolution protocol (ARP) request.

One of the functions the mesh node may perform when acting as a meshportal (connected to an AP) is to send proxy ARP replies on behalf ofmesh nodes that are reachable through the mesh portal. The mesh portalcan proxy ARP for those mesh nodes that it contains within itsforwarding table. In the exemplary mesh network 250 of FIG. 4, meshportal C 254-1 can respond when it receives an ARP request for the layer2 address of mesh node X 254-6. Mesh portal C 254-1 may send a proxy ARPreply with its own physical address.

In step 482, node A 256 sends a 2-address packet to AP 252-1. Thispacket designates mesh portal C 254-1 as the destination because meshportal C 254-1 responded to the ARP request on behalf of mesh node X254-6. In step 484, AP 252-1 determines that mesh portal C 254-1 isaccessible via the IEEE 802.11 infrastructure interface 364 of AP 252-1.In step 486, AP 252-1 sends a 3-address IEEE 802.11 packet to meshportal C 254-1. In step 488, mesh portal C 254-1 analyzes the layer 3header of the packet and determines that the actual destination of thepacket is mesh node X 254-6.

In step 490, mesh portal C 254-1 determines that mesh node X 254-6 isaccessible via the 802.11mm interface 352. In step 492, mesh portal C254-1 determines the first hop on the best route to mesh node X 254-6,which may be mesh node D 254-5. In step 494, mesh portal C 254-1 sends a4-address IEEE 802.11 packet to mesh node D 254-5. In step 496, meshnode D 254-5 sends a 4-address IEEE 802.11 packet to mesh node X 254-6,and control ends.

Referring now to FIG. 8, a functional block diagram depicts a networkmodule 500 of an exemplary mesh node according to the principles of thepresent disclosure. The network module 500 includes a wireless interface502, which communicates with a physical layer (PHY) dispatcher 504. ThePHY dispatcher 504 communicates with an infrastructure mode IEEE 802.11media access controller (MAC) 506 and an 802.11mm MAC 508.

The infrastructure mode IEEE 802.11 MAC 506 communicates with a statemachine module 510 that controls infrastructure client association andauthorization. The 802.11mm MAC 508 communicates with a mesh routingprotocol module 512 and a forwarding table 514, which also communicatewith each other. The infrastructure mode and 802.11mm MACs 506 and 508each communicate with a host dispatcher 516. The host dispatcher 516includes infrastructure bridge and mesh bridge tables, which indicatewhether destination addresses are serviced by the infrastructure mode or802.11mm MACs 506 and 508, respectively.

An IEEE 802.11 host driver 518 communicates with the host dispatcher 516and the forwarding table 514. The IEEE 802.11 host driver 518communicates with a host (not shown), such as a laptop computer orportable media player. When the mesh node is not acting as a meshportal, the infrastructure mode IEEE 802.11 MAC 506 and the statemachine module 510 may be deactivated.

Referring now to FIG. 9, a flowchart depicts exemplary operation of thenetwork module 500 when transmitting a packet. Control begins in step550, where the host dispatcher 516 receives a packet. Control continuesin step 552, where the host dispatcher 516 determines whether thepacket's destination address is in the mesh bridge table. If so, controltransfers to step 554; otherwise, control transfers to step 556.

In step 554, the host dispatcher 516 sends the packet to the 802.11mmMAC 508. Control then continues in step 558, where the 802.11mm MAC 508requests next hop information from the forwarding table (FWT) 514. Instep 560, if there is an entry for this destination address in the FWT514, control transfers to step 562; otherwise, control transfers to step564.

In step 564, the 802.11mm MAC 508 requests the mesh routing protocolmodule 512 to begin route discovery to the destination address. Controlcontinues in step 566, where control determines if route discovery hascompleted. If so, control returns to step 558; otherwise, controltransfers to step 568.

In step 568, control determines whether a route discovery timeout haselapsed. Route discovery may fail, for example, if the destination nodeis asleep or no longer within the mesh network. If the route discoverytimeout has elapsed, control may signal a routing failure andsubsequently end; otherwise, control returns to step 566.

In step 562, an entry for the address has been found in the forwardingtable 514, and a 4-address 802.11mm packet is created. Control thencontinues in step 570. Referring now to step 556, control determineswhether the destination address is contained in the infrastructurebridge table. If so, control continues in step 572; otherwise, controltransfers to step 574. In step 574, route discovery is begun. Controltransfers to step 576. If route discovery has completed, control returnsto step 552; otherwise, control continues in step 578. In step 578,control determines if a route discovery timeout has elapsed.

If the route discovery timeout has elapsed, the packet destination islikely not in the mesh network, so control transfers to step 572 toforward the packet to the AP. Otherwise, control returns to step 576. Invarious implementations, control transfers to step 572 while stillwaiting for route discovery to complete or time out. In this way, thepacket can be forwarded to the infrastructure network without waitingfor route discovery to complete. If the packet's destination is found onone of the networks, route discovery may be abandoned on the other.

In step 572, the packet is sent to the infrastructure mode IEEE 802.11MAC 506. Control continues in step 580, where a 3-address packet iscreated and control continues in step 570. In step 570, the createdpacket is sent to the PHY dispatcher 504. Control continues in step 582,where the wireless interface 502 transmits the packet. Control thenends.

Referring now to FIG. 10, a flowchart depicts exemplary operation of thenetwork module 500 when receiving a packet. Control begins in step 600,where the PHY dispatcher 504 receives a packet from the wirelessinterface 502. Control continues in step 602, where control determineswhether the packet is from the mesh interface or from the infrastructureinterface. In various implementations, this is determined by examiningthe BSSID of the packet.

In various implementations, the ToDs and FromDs fields indicate whetherthe packet is a mesh packet or an infrastructure packet. Setting bothToDs and FromDs to one, which is normally reserved for a distributionsystem (DS) packet, may signify a mesh packet. In keeping with IEEE802.11, a ToDs of 0 and a FromDs of 1 may indicate that the packet isarriving from an AP. If the packet is a mesh packet, control transfersto step 604; otherwise, the packet is an infrastructure packet, andcontrol transfers to step 606.

In step 604, the packet is sent to the 802.11mm MAC 508. Controlcontinues in step 608, where the mesh mode bridge table may be updatedbased upon data, such as a source address, within the received packet.Control continues in step 610, where the entry in the forwarding table514 corresponding to the transmitter address of the received packet isupdated with the signal to noise ratio (SNR) experienced by the receivedpacket. Control continues in step 612.

In step 612, control determines whether the packet is a route discoverypacket. If so, control transfers to step 614; otherwise, controltransfers to step 616. In step 614, control determines what type ofroute discovery packet the current packet is. If the packet is a routerequest (RREQ) packet, control continues with the RREQ handling flowpresented below with respect to FIG. 14. If the packet is a route reply(RREP) packet, control continues with the RREP handling flow presentedbelow with respect to FIG. 16. In various implementations, other typesof route discovery packets can be accommodated.

Referring now to step 606, the packet is sent to the infrastructure modeIEEE 802.11 MAC 506. Control continues in step 618, where theinfrastructure bridge table may be updated to reflect informationobtained from the packet, such as a source address. Control continues instep 616. In step 612, the packet is sent to the host dispatcher 516.

Control continues in step 620, where the host dispatcher 516 determineswhether the packet's destination address matches the network address ofthe network module 500. If so, the packet has arrived at itsdestination, and control transfers to step 622; otherwise, the packet isforwarded according to the transmission flowchart of FIG. 9. In step622, the packet is sent to the IEEE 802.11 host driver 518, and controlends.

Referring now to FIG. 11, a graphical and tabular representation of anexemplary route discovery process is presented. An exemplary meshnetwork 640 includes nodes A, B, C, D, and E. The nodes are functionallyarranged in a line, with each node able to communicate with the neighboron either side. If node A wants to determine a route to node E, node Acan broadcast a route request (RREQ) with a destination address of E.

This RREQ is received by node B, and is broadcast by node B and receivedby node C. Node C broadcasts an RREQ, received by node D, and node Dbroadcasts an RREQ, received by node E. Upon receiving the RREQ, node Etransmits a route reply (RREP) to node A along a path opposite to thatby which the RREQ was received. Table 642 presents exemplary RREQhandling by each node, and table 644 presents exemplary RREP handling byeach node.

Tables 642 and 644 include step numbers in a generally chronologicalorder. The steps progress from the original RREQ being generated to thefinal RREP being received. Within each step, the corresponding nodeperforms a series of operations. Beginning in step one, node A generatesan RREQ. The contents of the RREQ are shown in square brackets. Thetransmitter address is A, the source address is A, the destinationaddress is E, and the metric associated with the RREQ is α₁.

The metric is a measure of the quality of the link over which the RREQis being sent. In various implementations, the metric for a link isdetermined by the transmitting node and included in the RREQ prior totransmission. When the transmitting node determines the metric, themetric between two nodes may be asymmetrical.

The metric stored in the RREQ may be a combination of the link metricand a received metric. In this way, the metric stored in the RREQ is acumulative metric from the source of the route request to the currentnode. The link metric may depend upon a data rate achievable over thelink. When forwarding the RREQ, the node sets the metric field to be thelower of the metric received and the link metric. The lower metric ischosen because the lowest data rate link restricts the data rate of theentire route.

In various implementations, the metric may depend upon the amount ofpower required to transmit the RREQ to the receiving node and/or thebattery life of the transmitting node. The metric may represent acumulative energy cost of sending a representative packet (such as theRREQ). When forwarding the RREQ, the node may then set the metric fieldto be the sum of the metric received and the link metric. The linkmetric may represent an energy cost for transmitting from the currentnode, and may be determined by the following equation:

${EnergyCost} = \frac{\begin{matrix}{\sum\limits_{retransmissions}{{ScalingFactor}\mspace{11mu} ({retransmission}) \times}} \\{{XmitPwr}\mspace{11mu} ({Rate}) \times {duration}\mspace{11mu} ({Rate})}\end{matrix}}{{cost}\mspace{11mu} ({BatteryCondition})}$

The equation sums the energy cost for the initial transmission and anyretransmissions. A node may transmit the RREQ at a first power level,and then retransmit the RREQ at increasing power levels. The metric willtherefore be different for each of the transmitted RREQs. The first RREQreceived by a neighbor node will contain the lowest metric RREQ that theneighbor node was able to receive.

The ScalingFactor( ) function depends upon the retransmission number,and may decrease from one as the retransmission number increases. TheXmitPwr( ) function depends upon data rate, returns the amount of powerexpended during transmission per unit of time, and increases as the datarate increases. The duration( ) function depends upon data rate, returnsthe amount of time required to transmit the representative packet, anddecreases as the data rate increases. The cost( ) function depends uponthe condition of the node's battery, and decreases as the node'sremaining battery life decreases.

The amount of influence the battery condition has on the cost( )function determines how heavily battery life will affect the reportedenergy cost of the present node. When an energy cost metric is employed,the best route can be determined by selecting the route with the lowestenergy cost. When a node receives multiple RREQs, the node may selectthe RREQ with the lowest energy cost, add the energy cost for thecurrent link, and transmit the resulting RREQ.

Referring again to step one of table 642, the RREQ with metric α₁ isbroadcast from node A to the broadcast address (*), as indicated withinthe curly braces. In the next operation, node A creates a new RREQ withan updated metric α₂, and broadcasts this RREQ. Node A continuesbroadcasting RREQs until a final RREQ with metric α_(N) is broadcast.The RREQs may be broadcast with increasing power. This increasing powerrequired to transmit the RREQ may be reflected in an increasing metric.

The metric α₁ may include the power required to transmit the RREQdivided by the battery state of node A. Likewise, the metric α₂ mayinclude the power required to transmit the second RREQ divided by thebattery state of node A. The metric α₂ will likely be greater than themetric α₁, as the transmit power increases and the battery state of nodeA remains the same or decreases.

In step two, node B receives one of the RREQs broadcast by node A. NodeB keeps the first RREQ received from node A and discards further RREQswith less preferable metrics. In this way, the stored RREQ contains thelowest possible metric able to reach node B. The metric received isdenoted by α_(a), which is one of the metrics from α₁ to α_(N).

Because connections are assumed to be bidirectional, the fact that anRREQ was received by node B from node A indicates that node B can alsotransmit a packet to node A. Node B may therefore create an entry in itsforwarding table (FWT) based on the received RREQ. The FWT entryincludes the source address A, a reverse status, the transmitter addressA, and the metric α_(a).

The FWT entry is labeled as a reverse route because the metric α_(a)received in the RREQ corresponds to the metric from node A to node B,not from node B to node A. For example, if metrics are dependent onbattery life, when nodes A and B have different battery lives, themetric from node A to node B will be different than the metric from nodeB to node A. The FWT entry therefore indicates that node B can reachnode A, but does not include the actual metric from node B to node A.

In the next operation, node B broadcasts an RREQ from node B to thebroadcast address (*), as indicated within the curly braces. Node B maydetermine a link metric for broadcasting the RREQ. The link metric maybe based upon the battery state of node B and the power required totransmit the RREQ. The link metric may be combined with the metricreceived in the RREQ from node A. If the metric for node B to broadcastthe RREQ is β₁, the total metric stored within the RREQ may be α_(a)+β₁.

Node B continues broadcasting RREQs with increasing power levels. Thefinal RREQ that is broadcast has a cumulative metric of α_(a)+β_(N).Note that the transmitter address of the RREQs is now B, while thesource and destination addresses remain A and E, respectively. In stepthree, node C receives one of the RREQs broadcast by node B.

The received metric is one of the cumulative metrics from α_(a)+β₁ toα_(a)+β_(N). The received metric is referred to as α_(a)+β_(b), whereβ_(b) is one of the link metrics from β₁ to β_(N). Node C adds a reverseFWT entry having a source address of node A, a transmitter address ofnode B, and a cumulative metric of α_(a)+β_(b). This FWT entry indicatesthat to reach node A, node C can transmit a packet to node B.

The reverse FWT entry indicates that a packet from node A to node C willexperience a metric of α_(a)+β_(b), though the metric from node C tonode A is unknown. Node C then broadcasts RREQs, adding its own metricbeginning with γ₁. In step four, node B receives an RREQ from node Chaving a metric of α_(a)+β_(b)+γ_(c). Node D adds a reverse FWT entryindicating that node A is reachable via node C, and stores the receivedmetric.

Node D then broadcasts RREQs, increasing the metric by δ₁ through δ_(N).In step five, node E receives an RREQ from node D having a metric ofα_(a)+β_(b)+γ_(c)+δ_(d). Node E adds a corresponding reverse FWT entryto A. Because the RREQ was destined for node E, node E responds to theRREQ with an RREP. Node E thus begins RREP operation, such as is shownin table 644.

In step five of table 644, node E determines the best route from node Ato node E. This may be done by selecting the reverse FWT entry to node Athat has the best metric. As the only reverse FWT entry having adestination address of node A in this example, the reverse FWT entryindicating node D as the next hop, with metric α_(a)+β_(b)+γ_(c)+δ_(d),is chosen.

Now that node E has determined the best route from node A to node E,node E can inform node A of the best route as well as the associatedmetric. Node E thus generates an RREP and transmits it to the next hopspecified by the selected reverse FWT entry, node D. The contents of theRREP are included in square brackets: node A is the destination address,node E is the source address, and the cumulative metric from node A tonode E is α_(a)+β_(b)+γ_(c)+δ_(d).

Node D receives the RREP and selects a corresponding reverse FWT entry.As explained in more detail below, additional information may be storedwith reverse FWT entries to ensure that the RREP is matched to thecorrect reverse FWT entry. If the reverse FWT entry matches the RREP, ametric from node D to node E can now be calculated. The metric from nodeA to node D is already stored in the reverse FWT entry asα_(a)+β_(b)+γ_(c). The metric from node A to node E is contained in theRREP: α_(a)+β_(b)+γ_(c)+δ_(d).

Therefore, the metric from node D to node E can be determined bysubtracting the metric from node A to node D from the metric from node Ato node E. A direct FWT entry is then created. The direct FWT entry hasa destination of node E with a next hop address of node E and a metricof δ_(d). This direct FWT entry could not have been added when node Dbroadcast the RREQs. Metrics including δ₁ to δ_(N) were broadcast, andthe RREP is necessary to indicate that node E received the RREQincluding the metric δ_(d).

An RREP is transmitted from node D to node C including the same sourceand destination addresses and cumulative metric as the RREP sent fromnode E. In various implementations, the RREPs also include the metricexperienced by the RREP en route from node E to node A. Node C matchesthe RREP to a reverse FWT entry having the same destination as the RREP,node A.

Node C also adds a direct FWT entry to node E via node D. Node C thentransmits an RREP to node B. Node B receives the RREP, matches the RREPto a reverse FWT entry, and creates a direct FWT entry to node E. Node Bthen transmits an RREP to node A. Node A receives the RREP and adds adirect FWT entry to node E. Now that route discovery is completed, nodeA knows that a packet for node E can be sent to node B, and thecumulative metric experienced to node E will be approximatelyα_(a)+β_(b)+γ_(c)+δ_(d).

Referring now to FIG. 12A, a graphical depiction of route discoverymessages in an exemplary mesh network 650 is depicted. The mesh network650 includes nodes W, X, Y, and Z. In the example shown in FIG. 12A,node W is seeking a route to node Z. Node W begins by creating an RREQhaving a source address of W and a destination address of Z.

Because node W is transmitting the RREQ, the transmitter address is nodeW. Node X receives RREQ_(A), and node Y receives RREQ_(B). RREQ_(A) andRREQ_(B) may correspond to different power-level transmissions, asdescribed in more detail in FIG. 11. Each route discovery packet isgraphically depicted as a curved line from the transmitter to thereceiver. The curved lines are labeled at their transmitter ends withexemplary link metric numbers.

For example, the metric for RREQ_(A) is 21, while the metric forRREQ_(B) is 13. In various implementations, RREQ_(B) was transmittedearlier and with a lower power (and therefore a lower metric) thanRREQ_(A). RREQ_(B) was received by node Y but may not have been receivedby node X because of node X's greater distance from node W. The routediscovery packets, including RREQ_(A) and RREQ_(B), are presented intabular form in table 652.

In various implementations, if node W has established communicationlinks with node X and node Y, RREQ packets may be unicast to nodes X andY. Power may be increased in the RREQs until the corresponding receiveracknowledges receipt of the RREQ.

After node Y receives RREQ_(B), node Y waits for a predetermined amountof time to see if RREQs are received via other routes from node W. Inthis example, node Y does not receive other RREQs during this window,and so determines that the best route from node W to node Y is directtransmission to node Y. Node Y then broadcasts its own increasingpower-level RREQs, including RREQ_(C) and RREQ_(D).

RREQ_(C) is received by node X, and may include a link metric of 5. Thetotal metric within RREQ_(C) is therefore 13+5, or 18. The link metricof 5 from node Y to node X may be a function of the power required totransmit RREQ_(C) and may also be a function of the battery state ofnode Y. RREQ_(D) is received by node Z and includes a metric of 24. Themetric of 24 includes the metric of 13 from node W to node Y and thelink metric of 11 from node Y to node Z.

Node X may still have been waiting for RREQs originating from node W toarrive via other routes. Node X has now received an RREQ via two routes:directly from node W, and via node Y. Node X determines that the routefrom node W to node Y to node X has a superior metric of 18 compared tothe route directly from node W to node X, which has a metric of 21. NodeX therefore generates RREQs including the better metric of 18.

RREQ_(E) may be received by both nodes Y and Z. RREQ_(E) includes theprevious metric of 18 plus the link metric of 5 for transmittingRREQ_(E), yielding a total metric of 23. Because node Y has alreadytransmitted an RREQ, node Y may discard any later received RREQs, suchas RREQ_(E). Before discarding RREQ_(E), node Y may update itsforwarding table, as shown in more detail with respect to FIG. 12B.

Node Z has now received two RREQs from node W with two differentmetrics, 23 and 24. Node Z selects the more favorable metric of 23,meaning that the best route from Node W to node Z is via nodes Y and X.Node Z transmits an RREP to the next hop along the reverse of the bestroute. Therefore RREP_(A) is sent from node Z to node X.

RREP_(A) includes the selected cumulative metric of 23. RREP_(A) mayalso include a metric experienced from node Z to node X. For example,this metric may be 9. Node X receives RREP_(A) and transmits RREP_(B) tothe next hop in the reverse of the best route from node W. Because theroute from node W through node Y is preferable to the route from node Wdirectly to node X, node X transmits RREP_(B) to node Y.

The link metric from node X to node Y has increased from 5 to 7. Themetric from node X to node Y may have increased, for example, because ofdiminishing battery power of node X. The metric in RREP_(B) is therefore9+7, or 16. Node Y receives RREP_(B) and transmits RREP_(C) to node W.RREP_(C) now includes the metric from node Z to node W, 21, and thecumulative metric experienced in the best route from node W to node Z,23.

Referring now to FIG. 12B, a tabular representation of forwarding table(FWT) entries made during the route discovery process of FIG. 12A ispresented. A table 654 includes FWT entries created during the routediscovery process listed in approximate chronological order. The nodewhose FWT is being updated is listed in the second column, while theroute discovery packet whose information is used to update the FWT islisted in column 1.

The entries in the FWT include a direct/reverse indicator, a destinationaddress, a next hop address, a metric, and a source sequence number(SSN) and/or expiration time. When RREQ_(A) is received by node X, nodeX creates a FWT entry indicating that node W (the destination address)is reachable via node W (the next hop address). The stored metric is 21.The FWT entry is listed as a reverse entry because the metric stored isfrom node W to node X and not from node X to node W.

RREQ_(A) includes an SSN from node W, represented as lower case w. TheSSN may be incremented for each route discovery process that node Winitiates. For example, the next route discovery that node W initiatesmay have an SSN of w+1. The SSN may be used, as described in furtherdetail below, to match RREPs with reverse FWT entries.

Row two indicates that node Y creates a FWT entry based upon informationin RREQ_(B). Similarly, node X creates a FWT entry based upon RREQ_(C).The FWT entry that node X creates indicates that node W is reachable vianode Y, with a reverse metric of 18. Node Z creates a FWT entry based onRREQ_(D), indicating that node W is reachable via node Y and the routehas a reverse metric of 24.

Node Y may then create a FWT entry based upon RREQ_(E), indicating thatnode W is reachable from node Y via node X with a reverse metric of 23.Node Z also creates a FWT entry based upon RREQ_(E) indicating that nodeW is reachable from node Y via node X with a reverse metric of 23. NodeZ now has two FWT entries (shown in rows 4 and 6) with a destination ofnode W. The preferable FWT entry has a metric of 23, and an associatednext hop of node X.

Node Z is the destination of the RREQs and therefore responds with anRREP. RREP_(A) is transmitted to the selected next hop, node X. RREP_(A)includes the best metric from node W to node Z. RREP_(A) includes theSSN of the RREQ packets, w, which may now be stored in the destinationsequence number (DSN) field of the RREP. In various implementations,node Z may store its own SSN, labeled z, in RREP_(A). Node Z mayincrement its SSN upon initiating a route discovery.

RREP_(A) may include the link metric experienced from node Z to node X,9 in this example. Node X may then create two FWT entries. One entry, areverse FWT entry, has a destination of node Z with a next hop of node Zand a reverse metric of 9. The SSN of the RREP, z, may be stored in thereverse FWT entry. Node Z may increment its SSN upon initiating a newroute discovery.

Node X also creates a direct FWT entry to node Z via node Z. First, nodeX matches RREP_(A) to a reverse FWT entry. Matching is necessary toaccurately calculate a direct metric. The matching reverse FWT entryincludes the metric from node W to node X, while RREP_(A) includes themetric from node W to node Z. The direct metric from node X to node Zcan therefore be calculated by subtracting the metric from W to X (18)from the metric from W to Z (23), yielding 5.

If the reverse FWT entry does not match RREP_(A), such as if it has beenreplaced by a subsequent route discovery request, the calculation willbe erroneous. In various implementations, the SSN of the reverse FWTentry is compared to the DSN of the RREP. In this example, the sequencenumbers match, and the direct metric calculation is successful.

Node X creates RREP_(B) and transmits it to node Y, the next hop in theselected reverse FWT entry. Node B creates two entries in its forwardingtable based upon RREP_(B), a reverse entry and a direct entry. Invarious implementations, direct FWT entries may include a decrementingexpiration timer and/or an expiration time.

In the example of table 654, an expiration timer of 120 minutes isdefined. The expiration timer may be decremented at periodic intervals.The expiration timeout may be decreased at predefined intervals.Alternately, expiration may be indicated by a stored time, with earliertimes corresponding to older entries. Expiration times and/or timers maybe tailored to fit the application in which the mesh network will beused. For example, in relatively static environments, timers may be onthe order of days, while in more dynamic environments, timers may be onthe order of seconds.

While reverse FWT entries are primarily used to match with RREPs, directFWT entries contain actual metrics that will be experienced along agiven route to a destination. Therefore, the most recent actual metricmay be the most useful, as it is the one most likely to be accurate.When determining how to reach a given destination, a node may choosebetween an FWT entry with a better metric and a more recent FWT entrythat is more likely to be accurate.

In various implementations, reverse FWT entries also include expirationtimers and/or times. In various implementations, reverse and/or directFWT entries include other indicators of timeliness, such as a creationtime and/or a sequence number. While reverse FWT entries do not includeaccurate metrics, they do indicate via what route a destination node isreachable. Reverse FWT entries may also then be used when transmittingdata packets.

Node Y transmits RREP_(C) to node W. Node W creates two FWT entries,corresponding to direct and reverse routes to node Z via node Y. Thecumulative channel metric from node W to node Z, 23, is stored in thedirect FWT entry. In various implementations, the reverse FWT entry isdiscarded because the direct FWT entry already includes the actualmetric to node Z.

RREP_(C) may also contain an accumulated metric from node Z to node W.This is the metric experienced on the reverse of the best route fromnode W to node Z. The reverse of the best route from node W to node Zmay not be the same as the best route from node Z to node W. However,the accumulated metric is an actual direct metric from node Z to node W.

In various implementations, node W can send a route acknowledgement(ACK) to node Z, informing node Z of this accumulated metric. The routeACK is sent along the best route as indicated by the FWT entries of nodeW, node Y, and node X. When node Z receives the route ACK, it can createa direct entry to node W. The direct entry is via node X and includesthe metric of 21.

Referring now to FIG. 13A, an exemplary format of an RREQ packet isdepicted. The RREQ includes a reserved 1-byte ID field and a 4-bytelength field. The RREQ includes a 1-byte mode flag bit field. Bit 0 ofthe mode flag indicates whether the RREQ is unicast (zero) or broadcast(one). Bit 1 indicates whether the RREQ is a mesh portal announcement.In various implementations, no RREP is generated in response to a meshportal announcement. Bits 2-7 are reserved. The RREQ includes a 1-bytetime-to-live (TTL) field indicating the maximum number of hops that theRREQ should be allowed to traverse.

The RREQ includes a 1-byte destination count field indicating the numberof destinations contained within the RREQ. In various implementations,the count field is fixed at one. The RREQ includes a 1-byte hop countfield, which counts the number of hops that the RREQ has traversed. Thishop count can be compared to the value in the TTL field to determinewhether to continue forwarding the RREQ. The RREQ includes a 2-byte RREQID field, which together with the source address field uniquelyidentifies the RREQ.

The RREQ includes a 6-byte source address field indicating the originalsource address of the node requesting the route discovery. The RREQincludes a 2-byte source sequence number (SSN) field. Each node storesits own SSN and increments the SSN each time the node requests a newroute discovery. The SSN can then be used to determine relative ages ofroute requests from the same source. The RREQ includes a 2-byte metricfield, which contains the cumulative combination of the metrics from thesource up to and including the link metric determined by the nodetransmitting this RREQ. The RREQ includes a 1-byte destination flag, ofwhich bits 2-7 are reserved.

Bit 0 of the destination flag is the destination only bit, whichindicates whether an intermediate node that already has an FWT entry forthe destination address should respond to the RREQ. A value of zeroindicates that the intermediate node should send a proxy route reply(RREP) based upon the entry in the intermediate node's forwarding table.A value of one indicates that only the final destination should reply toan RREQ.

Bit 1 of the destination flag is the always forward bit, which indicateswhether an intermediate note should forward the RREQ regardless ofwhether the node has responded with an RREP. A value of zero indicatesthat if the intermediate node has responded with an RREP, the nodeshould not then forward the RREQ. A one indicates that, regardless ofwhether the node responds with a proxy RREP, the RREQ should beforwarded on. The RREQ includes a 6-byte destination address thatindicates the destination node to which the best route is being found.The RREQ includes a reserved 2-byte destination sequence number.

Referring now to FIG. 13B, an exemplary format of an RREP packet ispresented. The RREP includes a reserved 1-byte ID field, a 4-byte lengthfield, and a reserved 1-byte mode flag field. The RREP also includes a1-byte TTL field, a 1-byte source count field, and a 1-byte hop countfield. In various implementations, the source count field is fixed atone. The RREP includes a 2-byte received channel metric field, whichcontains the value of the metric that was selected by the RREQdestination (and therefore, the source of the RREP) as the metric of thebest route.

The RREP includes a 2-byte RREP ID, which together with the destinationaddress uniquely identifies the RREP. The RREP includes a 6-bytedestination address indicating the final destination of the RREP, whichwas the source address in the RREQ. In various implementations, the RREPID is set equal to the RREQ ID of the RREQ to which the RREP isresponding.

The RREP includes a 2-byte destination sequence number (DSN) field. TheDSN field may be set to the SSN field of the RREQ to which the RREP isresponding. The DSN field can be used to match the RREP to storedreverse routes to accurately calculate intermediate metrics, asdescribed in more detail above.

The RREP includes a 2-byte metric field, which is a cumulativecombination of metrics from the source of the RREP up to and includingthe node transmitting the RREP. The RREP includes a 6-byte sourceaddress field indicating the original source of the RREP. A 2-bytesource sequence number (SSN) may be reserved or may be the SSN of theRREP source as used in route requests.

Referring now to FIG. 14, a flowchart depicts exemplary operation of amesh node in receiving an RREQ packet. Control begins in step 700. Whenan RREQ is received, control transfers to step 702; otherwise, controlremains in step 700. In step 702, a timer is started. In variousimplementations, multiple timers are used to track multiple ongoingroute discovery attempts. Control continues in step 704. In step 704,the forwarding table is updated based on the information contained inthe RREQ packet, as described in further detail above.

Control continues in step 708. In step 708, the timer is compared to aconfiguration parameter DELAY. If the timer is greater than or equal toDELAY, control transfers to step 710. Otherwise, control returns to step704, where the forwarding table is updated based upon any other receivedRREQs.

In step 710, the DELAY period has elapsed and any further RREQs from thesame route discovery process will be discarded. RREQs may be comparedbased upon source sequence number (SSN) and source address (SA). If theSSNs and SAs are the same, the RREQs are part of the same routediscovery process beginning at the same node. In variousimplementations, the RREQ ID is also used to compare RREQs.

Control continues in step 712, where the best reverse FWT entry for thesource address of the received RREQ is selected. The best reverse FWTentry corresponds to the RREQ that includes the best metric. If themetric measures power required, the best metric would be the lowestmetric. The best reverse FWT entry therefore corresponds to the pathusing the least energy from the route discoverer to the current node.

When the destination node is reached, the destination node also choosesthe reverse FWT entry having the best metric. In this way, the best pathfrom the route requestor to the destination node is found. In variousimplementations, all reverse entries are saved in case the path of thebest reverse FWT entry fails, such as by a node leaving the mesh ortransitioning to low power mode.

Control continues in step 714. if the current node is the finaldestination of the RREQ, control generates an RREP as described in FIG.15 and then ends. Otherwise, control transfers to step 716. In step 716,if the destination only bit of the RREQ destination flag is set, controltransfers to step 718; otherwise, control transfers to step 720.

In step 720, control determines whether a direct FWT entry for the RREQdestination address exists. If so, control generates an RREP asdescribed in FIG. 15 and then continues with step 722. In step 722, ifthe always forward bit of the destination flag is set, control transfersto step 723; otherwise, control ends. In step 723, control sets thedestination only bit of the RREQ. Once a node has responded with a proxyRREP, any future node other than the destination should not send furtherproxy RREPs. Control then continues in step 718.

In step 718, control determines whether the RREQ should continue to beforwarded. To prevent such effects as broadcast storms, the time-to-live(TTL) of the RREQ can be analyzed. For example, if the hop count of theRREQ is greater than the TTL of the RREQ, control ends; otherwise,control transfers to step 724. In various implementations, the TTL maybe decremented at each hop, and then compared to a value of zero.

In step 724, the value of hop count in the RREQ is incremented andcontrol continues in step 726. In step 726, the metric contained in theRREQ is updated based upon factors such as battery life of the presentnode, power required for transmitting the RREQ, and/or number ofretransmissions. Control continues in step 728, where control attemptsto broadcast the RREQ to neighboring nodes.

In step 730, if the maximum number of retransmissions has been reached,control ends; otherwise, control transfers to step 732. In step 732, thetransmission parameters of the RREQ are modified to increase thelikelihood that the RREQ is received by neighboring nodes. For example,transmission power may be increased and/or data rate may be decreased.

In various implementations, neighboring nodes are associated with thetransmitting nodes. Control may broadcast the RREQ at a power levelexpected to reach the neighboring nodes. Alternatively, a feedbackmechanism may be used, whereby the power level is increased untilneighboring nodes acknowledge receipt of the RREQ. In variousimplementations, these methods may be repeated in a unicast fashion foreach neighboring node.

Referring now to FIG. 15, a flowchart depicts exemplary operation of amesh node in generating an RREP packet. Control begins in step 750,where the mesh node creates an RREP having a destination address equalto the source address of the received RREQs. Control continues in step752, where the metric of the selected route (best reverse FWT entry) isstored in the received channel metric field of the RREP. Controlcontinues in step 754, where the metric field of the RREP is set basedupon transmission of the RREP.

The metric may be based upon the battery state of the current node, thedata rate available to send the RREP, and/or the power required to sendthe RREP (including retransmissions). Control continues in step 756,where the RREP is transmitted. In step 758, if the maximum number ofretransmissions has been reached, control ends; otherwise, controltransfers to step 760. In step 760, the transmission parameters for theRREP are modified to increase the likelihood that the RREP is received.The metric field of the RREP may also be updated, and control returns tostep 756.

Referring now to FIG. 16, a flowchart depicts exemplary operation of amesh node in receiving an RREP. Control begins in step 800, where thereceived RREP is matched to a reverse route based upon the RREPdestination address, the RREP ID, and/or the RREP destination sequencenumber (DSN). If the best next hop of the selected reverse route is notavailable, another reverse route with the same destination address maybe selected.

In step 802, control determines the intermediate metric from the currentnode to the RREQ destination. The metric from the RREQ source to thecurrent node was received before and stored in the FWT. The total metricfrom the RREQ source to the RREQ destination has been received in theRREP. The current node can therefore remove the metric up to the currentnode from the total metric to obtain the metric between the current nodeand the RREQ destination.

Control then updates the forwarding table in step 804 with thisinformation. Control may also create a reverse FWT entry based on theRREP. Control continues in step 806, by determining whether the currentmesh node was the original source of the RREQ. If so, this routediscovery has completed and control transfers to step 807; otherwise,control transfers to step 808. In step 807, control determines whetherto send a route acknowledgement (ACK). If so, control transfers to step809; otherwise, control ends. In step 809, control transmits a route ACKand then ends.

The route ACK includes the RREP metric as received at the RREPdestination, which is the metric from the RREP source to the RREPdestination. The route for this metric is the reverse of the best routefrom the RREQ source to the RREQ destination. If all links between nodesare symmetric, this reverse route will be the best route from the RREPsource to the RREP destination. The Route ACK provides the RREP sourcewith the metric to reach the RREP destination. The RREP source may usethis path to reach the RREP destination, allowing it to forego its ownroute discovery process.

Referring now to step 808, control compares the hop count of the RREP tothe TTL of the RREP. If the hop count exceeds the TTL, control ends;otherwise, control transfers to step 810. In step 810, the hop count isincremented. Control continues in step 812, where the metric of the RREPis updated. The metric may be updated based upon the parameters of theupcoming transmission of the RREP to the next node.

Control continues in step 814, where the RREP is forwarded to the nexthop indicated by the selected reverse FWT entry. In step 816, if themaximum number of retransmissions has been reached, control ends;otherwise, control transfers to step 818. In step 818, transmissionparameters for the RREP are updated to increase the likelihood of theRREP reaching neighboring nodes. The RREP metric may also be updated.Control then returns to step 812.

Referring now to FIG. 17, an exemplary implementation of a forwardingtable (FWT) is depicted. The FWT may be composed of two tables, adestination table 852 and a next hop table 854. Destination table 852includes sets of FWT data indexed by destination address. Multiple setsof FWT data may be stored for the same destination address, such asshown for destination addresses 1 and 4 in FIG. 17.

Multiple entries allow for a different route to be selected if thepreferred route is not available. Multiple entries may also allow fordirect and reverse entries for a destination to be storedsimultaneously. A field of each set of FWT data in the destination table852 points to an entry in the next hop table 854.

In various implementations, the entries within the next hop table 854are unique, with only one entry for each next hop. Multiple destinationtable entries may point to a single next hop entry, such as shown forFWT data 2, 4, and 7 in FIG. 17. The entries in the next hop table 854are updated when the corresponding next hop changes state. For instance,the next hop may disassociate itself from the mesh network or may enterlow-power mode.

When the corresponding entry in the next hop table 854 is updated, anycorresponding routes in the destination table 852 are updated becausethey point to this updated information. The forwarding table may beupdated in such instances as when beacons are received from aneighboring station, when a new data packet is received, when an RREQ orRREP is received, when a local link announcement is received, and when apeer disconnect message is received.

Referring now to FIG. 18, a more detailed depiction of forwarding tablecontents is shown. The destination table 852 includes entries having a6-byte destination address field that stores the final destinationaddress (such as MAC address) of the route. The destination tableentries include a 4-byte pointer field that points to a next hop entryin the next hop table 854 that corresponds to the best next hop to reachthe destination address.

The destination table entries include a 2-byte channel metric fieldindicating the expected metric to be experienced by a packet transmittedto the corresponding destination address. The destination table entriesinclude a 1-byte hop count field indicating the number of hops expectedin the specified route to the destination address. The destination tableentries include a 1-byte direction field that indicates whether theentry is a direct route with an actual metric or a reverse route with anestimated metric. The estimated metric will be more accurate when linksare more symmetric.

The destination table entries include a 2-byte sequence number field andan 8-byte lifetime field. The sequence number field may store sourcesequence numbers for reverse entries to allow matching with RREPs. Thelifetime field indicates the length of time that the entry in thedestination table 852 will remain valid. The entry may be removed fromthe destination table 852 after this period of time has elapsed. Thevalue in the lifetime field may be reset to a value determined by aFWT_ENTRY_LIFETIME parameter when a corresponding RREQ or RREP isreceived. As discussed above, the lifetime field may alternately specifya specific time when the FWT entry expires.

The next hop table 854 includes entries having a 6-byte next hop addressfield that stores the physical (MAC) address of the next hop. The nexthop table entries may include a 2-byte receiver signal-to-noise ratio(SNR) field, which stores the most recently measured SNR from thecurrent node to the specified next hop. The next hop table entries alsoinclude a 1-byte sleep mode state field. In various implementations, thesleep mode state field can assume values from zero through four,indicating various levels of power saving modes.

For instance, a value of zero in the sleep mode field may indicate thatno power saving is occurring at the next hop. A value of one mayindicate that the next hop is in a power save mode but is awake duringthe announcement traffic indication message (ATIM) window. A value oftwo may indicate that the next hop is in a power save mode and will beawake for the duration of the next beacon transmission.

A value of three in the sleep mode field may indicate that the next hopis in a low power mode, where it will receive packets but not forwardthem. A value of four may indicate that the next hop is in deep sleepmode, not awakening for multiple beacon intervals. The next hop tableentries may also include a field (that shown) that stores the number ofbeacon intervals before the next hop will awaken. This information maybe obtained from 802.11mm firmware. If the next hop is a mesh portal,the sleep mode state field will likely have a value of zero because meshportals remain awake to receive beacons from associated APs.

Referring now to FIG. 19, a table 880 graphically depicts exemplaryconfiguration parameters for operation of a mesh node according to theprinciples of the present disclosure. The table 880 includes aBATTERY_COST_FCT parameter, which is a scaling factor for the batterycondition when adjusting the channel metric. A greater value increasesthe sensitivity of the channel metric calculation to the batterycondition.

The table 880 includes a DELAY parameter, which indicates the amount oftime that a node should wait for further RREQ messages having the samesequence number and source address after receiving a first RREQ. Thetable 880 includes a MESH_PORT_ANN_DUR parameter, which specifies theinterval between mesh portal announcement messages. Mesh portalannouncements serve to appraise all the nodes in communication with themesh portal of the preferred route to the mesh portal. Mesh portalannouncement messages are indicated by a one in bit 1 of the mode flagof an RREQ packet.

The table 880 includes a BATTERY_COND_DUR parameter, which specifies howoften to determine the battery condition of the node. The table 880includes a MESH_METRIC_DLT parameter, which is a threshold thatdetermines selection of the appropriate next hop. The table 880 includesa PAGING_DUR parameter, which indicates the time (specified in beaconintervals) between awakening events when in deep sleep mode.

The table 880 includes PAG_INTVL, which indicates the duration the nodewill remain awake while in deep sleep mode in order to receive an RREQmessage. The table 880 includes a PAG_AWAKE_INTVL parameter, whichindicates the duration that the node will stay awake while in deep sleepmode to receive data after reception of an RREQ message.

The table 880 includes an RREQ_NUM_RETRANSMISSION parameter, whichindicates the number of times that a broadcast RREQ should beretransmitted. The table 880 includes a MAX_RETRANSMISSION parameter,which indicates the maximum number of times that a unicast packet shouldbe retransmitted. The table 880 includes an FWT_ENTRY_LIFETIMEparameter, which indicates the lifetime of an entry in the forwardingtable.

Referring now to FIGS. 20A-20C, various exemplary implementationsincorporating the teachings of the present disclosure are shown.Referring now to FIG. 20A, the teachings of the disclosure may beimplemented in a WLAN interface 952 of a vehicle 946. The vehicle 946may include a vehicle control system 947, a power supply 948, memory949, a storage device 950, and the WLAN interface 952 and associatedantenna 953. The vehicle control system 947 may be a powertrain controlsystem, a body control system, an entertainment control system, ananti-lock braking system (ABS), a navigation system, a telematicssystem, a lane departure system, an adaptive cruise control system, etc.

The vehicle control system 947 may communicate with one or more sensors954 and generate one or more output signals 956. The sensors 954 mayinclude temperature sensors, acceleration sensors, pressure sensors,rotational sensors, airflow sensors, etc. The output signals 956 maycontrol engine operating parameters, transmission operating parameters,suspension parameters, etc.

The power supply 948 provides power to the components of the vehicle946. The vehicle control system 947 may store data in memory 949 and/orthe storage device 950. Memory 949 may include random access memory(RAM) and/or nonvolatile memory such as flash memory, phase changememory, or multi-state memory, in which each memory cell has more thantwo states. The storage device 950 may include an optical storage drive,such as a DVD drive, and/or a hard disk drive (HDD). The vehicle controlsystem 947 may communicate externally using the WLAN interface 952.

Referring now to FIG. 20B, the teachings of the disclosure can beimplemented in a WLAN interface 968 of a cellular phone 958. Thecellular phone 958 includes a phone control module 960, a power supply962, memory 964, a storage device 966, a cellular network interface 967,and the WLAN interface 968 and associated antenna 969. The cellularphone 958 may include a microphone 970, an audio output 972 such as aspeaker and/or output jack, a display 974, and a user input device 976such as a keypad and/or pointing device.

The phone control module 960 may receive input signals from the cellularnetwork interface 967, the WLAN interface 968, the microphone 970,and/or the user input device 976. The phone control module 960 mayprocess signals, including encoding, decoding, filtering, and/orformatting, and generate output signals. The output signals may becommunicated to one or more of memory 964, the storage device 966, thecellular network interface 967, the WLAN interface 968, and the audiooutput 972.

Memory 964 may include random access memory (RAM) and/or nonvolatilememory such as flash memory, phase change memory, or multi-state memory,in which each memory cell has more than two states. The storage device966 may include an optical storage drive, such as a DVD drive, and/or ahard disk drive (HDD). The power supply 962 provides power to thecomponents of the cellular phone 958.

Referring now to FIG. 20C, the teachings of the disclosure can beimplemented in a WLAN interface 994 of a media player 989. The mediaplayer 989 may include a media player control module 990, a power supply991, memory 992, a storage device 993, the WLAN interface 994 andassociated antenna 995, and an external interface 999.

The media player control module 990 may receive input signals from theWLAN interface 994 and/or the external interface 999. The externalinterface 999 may include USB, infrared, and/or Ethernet. The inputsignals may include compressed audio and/or video, and may be compliantwith the MP3 format. Additionally, the media player control module 990may receive input from a user input 996 such as a keypad, touchpad, orindividual buttons. The media player control module 990 may processinput signals, including encoding, decoding, filtering, and/orformatting, and generate output signals.

The media player control module 990 may output audio signals to an audiooutput 997 and video signals to a display 998. The audio output 997 mayinclude a speaker and/or an output jack. The display 998 may present agraphical user interface, which may include menus, icons, etc. The powersupply 991 provides power to the components of the media player 989.Memory 992 may include random access memory (RAM) and/or nonvolatilememory such as flash memory, phase change memory, or multi-state memory,in which each memory cell has more than two states. The storage device993 may include an optical storage drive, such as a DVD drive, and/or ahard disk drive (HDD).

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the disclosure can beimplemented in a variety of forms. Therefore, while this disclosureincludes particular examples, the true scope of the disclosure shouldnot be so limited since other modifications will become apparent to theskilled practitioner upon a study of the drawings, the specification andthe following claims.

1. A wireless network device comprising: a forwarding table that storesdirect and reverse entries each including a destination address, a nexthop address, and a metric, wherein said metric of said direct entriescorresponds to a route from said wireless network device to saiddestination address, and wherein said metric of said reverse entriescorresponds to a route from said destination address to said wirelessnetwork device; and a mesh routing module that wirelessly receives routediscovery packets and that creates corresponding entries in saidforwarding table.
 2. The wireless network device of claim 1 wherein saidmesh routing module wirelessly receives a first route discovery packetincluding a metric and a source address from a second wireless networkdevice and creates a reverse entry in said forwarding table, whereinsaid next hop address of said reverse entry is set to an address of saidsecond wireless network device, said destination address of said reverseentry is set to said source address of said first route discoverypacket, and said metric of said reverse entry is set to said metric ofsaid first route discovery packet.
 3. The wireless network device ofclaim 2 wherein said mesh routing module wirelessly receives a routereply packet including a reply destination address, identifies ones ofsaid reverse entries that have said reply destination address, andtransmits said route reply packet to said next hop address of a selectedone of said identified reverse entries.
 4. The wireless network deviceof claim 3 wherein said mesh routing module selects said selected one ofsaid identified reverse entries based upon said metrics of saididentified reverse entries.
 5. The wireless network device of claim 3wherein said reverse entries each include a sequence number, and whereinsaid mesh routing module sets said sequence number of said reverse entryto a sequence number received in said first route discovery packet. 6.The wireless network device of claim 5 wherein said route reply packetincludes a reply sequence number, and wherein said mesh routing modulechooses ones of said identified reverse entries that have said replysequence number and selects one of said chosen reverse entries basedupon said metrics of said chosen reverse entries.
 7. The wirelessnetwork device of claim 1 wherein said mesh routing module receives aroute request for a requested destination address, identifies ones ofsaid direct entries that have said requested destination address, andselectively responds to said route request with said next hop address ofa selected one of said identified direct entries.
 8. The wirelessnetwork device of claim 7 wherein said mesh routing module selects saidselected one of said identified direct entries based upon said metricsof said identified direct entries.
 9. The wireless network device ofclaim 7 wherein said direct entries of said forwarding table include anexpiration indicator, and wherein said mesh routing module selects saidselected one of said identified direct entries based upon saidexpiration indicators of said identified direct entries.
 10. Thewireless network device of claim 1 wherein said mesh routing moduletransmits a route discovery packet including a cumulative metric to asecond wireless network device, determines said cumulative metric basedupon a received metric and a link metric, and determines said linkmetric based upon a state of charge of said wireless network device anda transmission parameter of said route discovery packet.
 11. Thewireless network device of claim 10 wherein said link metric increasesas said state of charge decreases.
 12. The wireless network device ofclaim 10 wherein said transmission parameter comprises energy used totransmit said route discovery packet.
 13. The wireless network device ofclaim 12 wherein said link metric is proportional to said energy usedand inversely related to said state of charge.
 14. The wireless networkdevice of claim 12 wherein said mesh routing module transmits said routediscovery packet using increasing amounts of energy.
 15. A method for awireless network device, comprising: wirelessly receiving routediscovery packets; and storing direct and reverse entries in aforwarding table based upon said route discovery packets, each of saidentries including a destination address, a next hop address, and ametric, wherein said metric of said direct entries corresponds to aroute from said wireless network device to said destination address, andwherein said metric of said reverse entries corresponds to a route fromsaid destination address to said wireless network device.
 16. The methodof claim 15 further comprising: receiving a first route discovery packetincluding a metric and a source address from a first wireless networkdevice; and creating a reverse entry in said forwarding table, whereinsaid next hop address of said reverse entry is set to an address of saidfirst wireless network device, said destination address of said reverseentry is set to said source address of said first route discoverypacket, and said metric of said reverse entry is set to said metric ofsaid first route discovery packet.
 17. The method of claim 16 furthercomprising: receiving a route reply packet including a reply destinationaddress wirelessly; identifying ones of said reverse entries that havesaid reply destination address; and transmitting said route reply packetto said next hop address of a selected one of said identified reverseentries.
 18. The method of claim 17 wherein said selected one of saididentified reverse entries is selected based upon said metrics of saididentified reverse entries.
 19. The method of claim 17 wherein saidreverse entries each include a sequence number, and further comprisingsetting said sequence number of said reverse entry to a sequence numberreceived in said first route discovery packet.
 20. The method of claim19 wherein said route reply packet includes a reply sequence number, andfurther comprising: choosing ones of said identified reverse entriesthat have said reply sequence number; and selecting one of said chosenreverse entries based upon said metrics of said chosen reverse entries.21. The method of claim 15 further comprising: receiving a route requestfor a requested destination address; identifying ones of said directentries that have said requested destination address; and selectivelyresponding to said route request with said next hop address of aselected one of said identified direct entries.
 22. The method of claim21 wherein said selected one of said identified direct entries isselected based upon said metrics of said identified direct entries. 23.The method of claim 21 wherein said direct entries of said forwardingtable include an expiration indicator, and wherein said selected one ofsaid identified direct entries is selected based upon said expirationindicators of said identified direct entries.
 24. The method of claim 15further comprising: receiving a first route discovery packet including ametric; determining a link metric based upon a state of charge of saidwireless network device and a transmission parameter of a second routediscovery packet; determining a cumulative metric based upon a receivedmetric and said link metric; and transmitting said second routediscovery packet wirelessly to a first wireless network device, saidsecond route discovery packet including said cumulative metric.
 25. Themethod of claim 24 wherein said link metric increases as said state ofcharge decreases.
 26. The method of claim 24 wherein said transmissionparameter comprises energy used to transmit said second route discoverypacket.
 27. The method of claim 26 wherein said link metric isproportional to said energy used and inversely related to said state ofcharge.
 28. The method of claim 26 further comprising transmitting saidsecond route discovery packet using increasing amounts of energy.